100 posts to pm.
the card acts as a dedicated physx card. so when a games is using physx, the card will do all of the processing and take a MASSIVE load off of the cpu. but only a small amount of games will use physx so unless you can get a great deal on a card, it probably isn't worth it.
with games that can use the physx card, you definitely can tell the difference seeing as how you can see the extra eye candy you normally can't with just an ati card.